1. Field of the Invention
This invention relates to methods of controlling vegetation, and particularly to the use of contact herbicides for the general or selective control of vegetation.
2. Description of the Art
Both urea and sulfuric acid are widely used for a variety of purposes in numerous industries as fertilizers, soil adjuvants, chemical treating agents, chemical precursors and reactants. They are sometimes useful in combination, particularly in the agricultural industry, when the simultaneous addition of urea and sulfur to the soil is desired. Sulfuric acid is known to be phytotoxic, has been used as a postemergent, contact herbicide on a variety of plants, and is registered with the U.S. Environmental Protection Agency for the elimination of certain weed plants from plots of growing onions and garlic.
It has also been disclosed that urea will react with sulfuric acid to produce combinations of urea and sulfuric acid that are useful as fertilizers and soil treating agents.
Although sulfuric acid is an effective contact herbicide, it is relatively nonselective in that it damages essentially all foliage it contacts, and it is rapidly consumed by reaction with plant tissue. Thus, substantial quantities of sulfuric acid are required to obtain any effective degree of vegetation control. Furthermore, sulfuric acid is highly corrosive to many materials, including animal tissue, and thus is difficult to transport and distribute and requires the strict observance of safety practices to prevent injury to personnel involved in its application.
Although some investigators have disclosed that certain combinations of urea and sulfuric acid can be manufactured, they have not disclosed any method capable of producing significant, if any, quantities of the higher acid content compositions which contain a significant amount of the monourea-sulfuric acid adduct. Nor were their processes capable of producing urea-sulfuric acid reaction products free of decomposition products. The decomposition of urea and sulfuric acid upon their interaction can result in the formation of toxic materials such as sulfamic acid and ammonium sulfamate which are undesirable in certain applications Such decomposition can invariably result in the loss of sulfuric acid activity due to conversion of the acid to sulfamic acid, ammonium sulfamate, ammonium sulfate or other decomposition products. The presence of such decomposition products in the herbicidal composition of this invention does not contribute to herbicidal activity and, in some instances, is undesirable.
Many contact herbicides other than sulfuric acid are known and are widely used for the control of vegetation. However, many if not all of these have significant ecotoxic effects and are relatively expensive to manufacture. Furthermore, few, if any, of the alternative herbicides contribute significant, if any, quantities of nutrients or beneficial soil adjuvants to the plant environment. Most alternative contact herbicides are also toxic to humans. Thus, their use requires the observance of safety precautions sufficient to avoid harm to personnel involved in their application. Accordingly, a need exists for improved methods of vegetation control that minimize or eliminate these and other deficiencies of existing methods.
It is, therefore, a principal object of this invention to provide improved methods of vegetation control.
Another object of this invention is the provision of methods of vegetation control that are relatively nonhazardous to applicators and to the environment.
Another object is the provision of methods of vegetation control that result in the addition of significant amounts of plant nutrients and beneficial soil adjuvants to the plant environment.
Another object of this invention is the provision of methods for selectively eliminating undesired vegetation from the vicinity of desired vegetation.
Another object is the provision of methods for controlling undesired vegetation that do not result in the addition of toxic materials to the environment or to crops growing or subsequently planted in the treated area.
Another object is the provision of methods for controlling undesired vegetation that are more efficient than previously available methods and that thereby reduce the cost of controlling such vegetation.
Another object is the provision of methods for controlling undesired vegetation in the vicinity of a seeded crop prior to emergence of the crop without damage to the crop seeds or seedlings.
Other objects, aspects and advantages of this invention will be apparent to one skilled in the art in view of the following disclosure, the drawings and the appended claims.